Off-peak electric water heating system



NOV 24, 1953 J. K.'osTRANDER 2,650,657

oFF-PEAK ELECTRIC WATER HEATING SYSTEM JNVENTOR. Joiisf'nder, BY

@i6 fg ATTORNEYS.

Nov. 24, 1953 1. K. osTRANDl-:R 2,660,657

OFF-PEAK ELECTRIC WATER HEATING SYSTEM Filed May 25, 1952 2 Sheets-Sheet 2 IN VEN TOR. J a/m fr. 0.9 ira/miei:

ATTORNEYS Patented Nov. 24, 1953 OFF-BEAI ELECTRIC WATER HEATING SYSTE John-K'. Ostrander, Philadelphia, Pa.

Application MayV 23, 1952, Serial No. 289,508

(Cl. 21S-38) 1 Claim. 1

This invention relatesv to ofpeak water heating,

systems in which the heating is accomplished electrically.

The chief aim ofmy invention is to provide a simple and reliablesystem for automatically controlling the supply of electric power to domestic water heaters soy that a desired daily load curve willbe obtained forthe power line to which the4 heater is connected, and to make possible thereby, the use of smaller sizes of water tanks for the heaters.

Other objects andattendant advantages. will appear from the following detailed description of. theattached drawings wherein:

Fig. l is aview in axial section of an upright tank of the type ordinarily employed to supply hot'water'for domestic purposes, with incorporated automatically-controlled electric heating means conveniently embodying my invention.

'Fig'. 2 is a .fragmentary View in horizontal section 4taken asy indicated bythe angled arrows II-Il in Fig. 1.

3 is a wiring diagram of the various instrumentalities of an automatic system by which the heating of the, water in the tank is controlled in accordance with myinvention, the system being here illustrated in dormant condition.

Fig. ll is a View like Fig. 3 showing the system.

in one of' its active phases.v

`The ltank illustrated in Figs. 1 and'Z is of standard-construction in that it has an upright cylindric metallic shell 5 with a cold water inlet 'Sat the bottom and with a hot water outlet l at the-top. For theepurposes of heat'conservation, the Shelli is provided as` usual with a jacket 8 ofsuitable thermal insulation. Atl'rin Fig. l,4

is indicated theelectric resistance coilelement for heating" the'water which, after customary practice, i's` disposed horizontally adjacent the bottom of the tank.

Rigidly secured'in accordance with my invention, to the side of the shell 5 immediately above heating element I and extending approximately uprto'themid height of the tank is a relatively thickplate ll of metal or the like having a high coeiicient of thermal conductivity whereon are mounted adjacent the top and bottom, thermostat switches l2 and I3v respectively. As shown, the heating element I0 and the thermostat I2 and l'3 are accessible for inspection or for replacement, when necessary, upon removal of a protective door l fromfan opening IB in the insulation jacket 8. suitably secured crosswise of the inside lof the tank-shell 5 in the region of the plate lIginlaccordancewithmy invention, is a vertical diaphragm I1 which, in practice, is fashioned.. from non-metallicmaterial. such as wood or plastic ,`low in thermal conductivity and which sets apart a narrow upright water channel within the tank shell at that region.

The means which I have devised for automatically controlling heating of the water in the tank includes. as shown in Fig. 3, a timer I8 which maybe ofy the type having a shaft i8 driven, through worm gearing from an electric motor 2| so as to be turned' through a single rotation once. in every twenty-four hours. Mounted on shaft i9 are rotary cams with rises 22 and 23 for, respectively actuating the timer switchesV designated 25 and 26. As shown, the cams 22V and 2?;.are so set upon shaft l@ to permit closing of the switches 25 and 26 at different times, the former for example at 10:00 p. in. and the latter at 3:0@ a. m. Also included in my improved control is a relay switch 2l. Motor 2l is connected directly across the mains 23 and 29 of a power supply line so as to be in continual operation.`

Extending from power main 28 to one terminal of heating coil ES are conductors 36 and 3l, the other end of said coil being connected through conductors Stand 33 to one end of the coil 34 of relay 2l. The other terminal of lrelay coil 34 is connected to conductor 3Q by a wire 35; A lead 355 extends from main 29 to one contact 31' of timer switch 25, the other Contact 33 of said switch being connected through wire 39 and branches eiland il of the latter to the contacts and i3 respectively of thermostat I2 and of relay switch 2l; One Contact 45 of timer switch 26 is connected by a lead 46 to conductor 39, and the other contact di of said switch by a lead 48 and branches 69 and 5S of the latter respectively to the contacts 6l and 52 of the thermostats l2 and i3. and 61?',y the contacts 55 and 56 respectively of' thermostat i3 and relay switch 2l are connected to conductors 33 and it.

Operation If,when the tank is filled withhot water, 'some of the hot water is withdrawn at the top through outlet l,v a corresponding amount of cold waterwillv enter at the bottom` through inlet in the knownv manner, with establishment of a fairly distinct line oi' demarcation between the hot and. cold stratascr zones at the con'ipletion of the draft. During the period, say between 6:00 a; m.

andr 10:60 p. in. representingthe peak hours inthe consumption of electricity. fromthe power line, the control. system will be inthe dormant condition in which it is shown in 3, i. with; the switches 25, 25 held open by the cams 22 andE 'Under this condition, no current.

Through addtional'branch wires 53' accuser mostat I2 will be under the influence of the temperature of the cold water say at 150 degees above level A and will thus be closed as in Fig. e. On the other hand, if at :00 p. m., the cold water reaches up to the level B only, the thermostat I2 will be open, but heat will begin to pass from the water within the upper end of channel C into the upper end of plate I l and down the plate into the water in the lower end of said channel. Consequently, the temperature of the water in the upper part of channel C will gradually fall even though no more hot water is withdrawn. In this way, heat is transmitted from the upper end of the channel to the lower end. However, as the averagc `temperature of the water in the tank is not chf. D'ed to any great extent, very little pressure is created in the channel so that very little movemeiit of water will take place. The temperature ci' the water in the channel iinally will become nearly uniform from top to bottom, thereby causing the temperature at the thermostat I2 to be nearly equal to the average ternperature of the water on the outside surface ci diaphragm Il. Accordingly, the temperature of the thermostat i2 .,irill gradually fall and said thermostat will close as in Fig. fl even though the cold water lef/el is only at B. The time required for closing will be proportional to the amount of hot water on the outer surface of diaphragm Il or the amount of hot water in the tank. Upon closing of thermostat i2, which will be assumed to function at 100 degrees, current will ilow from main 2S, conductors 3i: and 3i, heating element I il, conductors S2 and 53, closed thermostat I3.

conductors 50 and 49, thermostat l2, conductors 40 and 39, switch 25, and conductor 36 to main 29. At the same time, current will pass by way of conductors 35 and 33 through coil 34 ci relay 21, thereby closing the latter with attendant shunting of thermostat I2. tions, the temperature of the cold water in the bottom of the tank will rise until it has reached say 100 degrees, i. e., sufficient to open thermostat I2, and relay 2l will remain closed to hold the circuit through resistance element Ill for con tinued heating of the water. When the entire contents of the tank is eventually heated, thermostat I3 will open and the system will be thereby restored to dormant condition.

When heating element I S is energized, the temperature of the body of cold water will rise without much variation in temperature between parts of the cold water section. The temperature of the water in the channel C behind the diaphragm I'I will be approximately equal to the temperature of the water on the other side oi' the diaphragm. Therefore, the contacts of the upper thermostat i2 will open whenever the temperature or the body of cold water reaches a predetermined value, such as 10G degrees, but as the current is shunted around the contacts of thermostat I2 by relay 2l, current will continue to ilow until it is interrupted by opening of the contact of thermostat I3 without time delay as a result of the water temperature at the bottom of the tank reaching 150 degrees. Thus, with the described construction there will be a time lag in closing of the contacts of the upper thermostat i2 but no time lag in the opening of said contacts.

At 3:00 a. m., timer switch 2E will close upon advance of the rise of cam 23 beneath the shoe on contact 45 of said switch. If there is any cold water in the tank at this time with the lower thermostat I3 closed, heating element will be en- Under these condi- 2 ergized immediately to begin heating the water as will be readily understood by reference to the diagram of Fig. 4.

Relay switch 21 may have a voltage operating coil shown in Figs. 3 and l or it may have a series coil either of which become energized when current flows through heating element IU. The function of relay switch 2'! is to transfer control of the heating element IG from the upper thermostat I2 to the lower thermostat I 3 whenever the contacts of the upper thermostat close7 either by establishing a shunt circuit across the contacts of the upper thermostat or by holding contacts of this thermostat closed. As the temperature setting of lower thermostat I3 will be higher than that of upper thermostat I2, the temperature of the water will he determined solely by the lower thermostat. Therefore temperature adjustinents of lower thermostat I3 can be made without the necessity or making any changes to upper thermostat i2. Accordingly, the upper thermostat I2 may be simpler construction than that of lower thermostat I3 because it is never required to interrupt the current.

From the foregoing it will be seen that, with my improved system in operation in connection with multiple heaters, those heaters wherein the cold water reaches the level A will vbe energized at the early time (10H20 p. m.) when the timer switch 25 closes. Other heaters containing a lesser amount of cold water will he energized between the time that contact 37 of switch 25 closes and the time at which contact 45 of switch 26 closes. Consequently the energizing of many heaters will be delayed for a period of time proportional to the amount of water in the tanks.

Having thus described my invention, I claim:

An automatic olli-peak system for controlling the heating of water in a hot water supply tank having a cold water inlet at the bottom, a hot water outlet at the top, and an electric heating element in the bottom, said system including a thermal conductive plate attached to the outer surface of the tank shell and extending partway of the height of the latter from a point immediately above the level of the heating element; a diaphragm constructed of a material low in thermal conductivity and providing a narrow upright water channel within the tank in the region of the said plate; a thermostat switch mounted adjacent the bottom of said plate; a second thermostat switch with a lower temperature setting mounted adjacent the top of said plate at an intermediate level in the tank; a continually operating timer with two switches interposed respectively with the thermostatic switches and the heating element in interlocied circuits; and a relay actuated upon closing of the upper of the two thermostat switches for closing the corresponding timer switch, thereby to establish the circuit controlled by said timer switch and to thereafter hold said circuit closed, notwithstanding opening of said upper thermostat switch, until the lower thermostat switch opens when all of the Water in the tank is heated.

JOHN PI. OSTRANDER. References Cited in the ille of this patent UNITED STATES PATENTS 

